Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define P pair<int,int>

char grid[55][55];
int dist[55][55];
const int INF=INT_MAX;
int di[]={0,1,0,-1};
int dj[]={1,0,-1,0};

int main(){
  int h,w;
  cin>>h>>w;
  int black=0;
  rep(i,h)rep(j,w){
    cin>>grid[i][j];
    dist[i][j]=INF;
    if(grid[i][j]=='#') black++;
  }
  dist[0][0]=0;
  queue<P> q;
  q.push(make_pair(0,0));
  while(!q.empty()){
    int pi,pj;
    tie(pi,pj)=q.front(); q.pop();
    int past = dist[pi][pj];
    rep(tmp,4){
      int now=past+1;
      int ni=pi+di[tmp],nj=pj+dj[tmp];
      if(grid[ni][nj]=='#') continue;
      if(ni<0 || ni>=h || nj<0 || nj>=w) continue;
      if(dist[ni][nj]<=now) continue;
      dist[ni][nj]=now;
      q.push(make_pair(ni,nj));
    }
  }
  if(dist[h-1][w-1]!=INF) cout<<h*w-black-dist[h-1][w-1]-1<<endl;
  else cout<<-1<<endl;
}